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.. _mpi_comm_rank:
MPI_Comm_rank
=============
.. include_body
:ref:`MPI_Comm_rank` |mdash| Determines the rank of the calling process in the
communicator.
SYNTAX
------
C Syntax
^^^^^^^^
.. code-block:: c
#include <mpi.h>
int MPI_Comm_rank(MPI_Comm comm, int *rank)
Fortran Syntax
^^^^^^^^^^^^^^
.. code-block:: fortran
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_RANK(COMM, RANK, IERROR)
INTEGER COMM, RANK, IERROR
Fortran 2008 Syntax
^^^^^^^^^^^^^^^^^^^
.. code-block:: fortran
USE mpi_f08
MPI_Comm_rank(comm, rank, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm
INTEGER, INTENT(OUT) :: rank
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
INPUT PARAMETERS
----------------
* ``comm``: Communicator (handle).
OUTPUT PARAMETERS
-----------------
* ``rank``: Rank of the calling process in group of comm (integer).
* ``ierror``: Fortran only: Error status (integer).
DESCRIPTION
-----------
This function gives the rank of the process in the particular
communicator's group. It is equivalent to accessing the communicator's
group with :ref:`MPI_Comm_group`, computing the rank using :ref:`MPI_Group_rank`, and
then freeing the temporary group via :ref:`MPI_Group_free`.
Many programs will be written with the manager-worker model, where one
process (such as the rank-zero process) will play a supervisory role,
and the other processes will serve as compute nodes. In this framework,
:ref:`MPI_Comm_size` and :ref:`MPI_Comm_rank` are useful for determining the roles of
the various processes of a communicator.
ERRORS
------
.. include:: ./ERRORS.rst
.. seealso::
* :ref:`MPI_Comm_group`
* :ref:`MPI_Comm_size`
* :ref:`MPI_Comm_compare`
|
